Tachometer.



P. VAN S. KOLFF & 1. E. HOLLYDAY. TACHOMETER.

APPLICATION FILED SEPT. I4. 1914.

191489692@ I Patented Aug. 3, 1915.

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PETRUS VAN SANTEN KOLFF, OF IVIOYLAN, AND JAMES E. HOLLYDAY, OFPHILADEL- PHIA, PENNSYLVANIA, ASSIGNORS TO THE ELECTRIC TACHOMETERCOMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION 0F NEW JERSEY.

TACHOMETER.

Specification of Letters Patent.

Patented Aug. 3, 1915.

Application filed September 14, 1914. SerialNo. 861,565.

To all whom it may concern Bc it known that we, (1) PETRUS VAN SANTENKoLrF and (2) J AMES E. HOLLYDAY, citizens of the United States,residing at (l) Moylan and (2.) Philadelphia, in the counties of (1)Delaware and (2) Philadelphia, and State of (1 and 2) Pennsylvania, haveinvented certain new and useful Improvements in Tachometers, of whichthe following is a specification.

This invention relates to tachometers particularly intended for use onships and is designed to enable a number of indicating instruments to beconnected to the same electric generator.

On ship-board it is desirable to locate the indicators in various partsof the vessel, such as the bridge, chart-house, and engineroom, and itis the object of this invention to make possible the use of two or moreindicators in circuit with the same generator and at the same time toprovide means whereby, should one or more indicators 'be out ofcommission, the remaining indicators will still `be kept in servicewithout affecting the accuracy of their indications.

Referring to the drawingsFigure 1 is a diagram showing the connectionswhen the indicators are connected in series with the generator; and Fig.2 is a diagram showing the connections when the indicators are connectedin parallel to the generator.

The system heretofore in use comprises an electric generator preferablyof the directcurrent .type driven from the shaft or other rotatingobject whose speed of motion is to be indicated, the current generatedbeing delivered to an indicating galvanometer. In the present system, agenerator G is connected to several indicators by means of a system ofswitches and calibrating resistances, all of which are located atl oneplace and preferably within a boX or chamber B.

Referring to Fig. 1, the diagram shows anv arrangement' in which theindicators are connected in series with each other and the generator,Iand this is the preferred system, as the error due to local variationsin temperature is distributed over the entire construction, and all theindicators will give like readings under all conditions of temperaturevariations. 'In this series system, the connections are from generatorGr through wire 1, variable calibrating resistance R, j

wire 23, indicator I1, wire 24, switch S1, wire 25, indicator I2, wire26,'switch S2, wire 27, indicator I3, wire 28, switch S3, wire 29, backto the-generator. Separate connecting wires 31, 32, and 33 connect wires23, 25, and 27, through variable resistances R1, R2, R3, to theterminals 41, 42', 43, of the doublethrow switches S1, S2, S3, so thatwhen any one of the switches is turned, the corresponding-indicator willbe cut out and an equivalent resistance included in the circuit.

Referring to Fig. 2, which illustrates the parallel system ofconnection, the circuit is from the generator G through wire 1 to themain calibrating variable resistance R, thence to the common wire 2,through Wires 3, 4, 5, indicators Il, I2, I3, back through connections6, 7, 8, to the variable calibrating resistances r1, r2, r3, to theterminals 9, 10, 11 of the double-throw switches S1, S2, S3, thence fromthe switches through wires 12, 13, 14, common return wire 15, to thegenerator.

Should any accident happen to one of the indicators, as for example Il,the corresponding switch S1 is shifted tol out out the indicator and toinclude instead the resistance R1. These resistances R1, R2, R3, in boththe systems referred to, are each so adjusted as to exactly correspondto the resistances of the particular indicator circuit to which it is tobe connected.

By means of the main calibrating resistance R and the Ismall resistancesr1, r2, r3, the system as a whole, and the individual circuits, can beaccurately adjusted to produce the requisite current in the indicator togive a full scaledeflection of the pointer.

. We claim:

1. An electric tachometer system, comprising a generator, a number ofindicating instruments in circuit with said generator, a like number ofresistances each equivalent to an indicating instrument, and means forcutting out any one of said instruments and for inserting an equivalentresistance, whereby the calibration ofthe systeml is maintained.

2. An electric tachometer system, comprising a generator, a number ofindicating instruments, in 'series circuit with said genarateresistance-including connections, each switch being arranged to out inone of said generator connected in series with said indif caters, and aCalibrating resistance in the generator circuit. A

In testimonv whereof, We aiiX our signa-A l tures in presence oftwoWitnesses.

PETRUS 'VAN SANTEN KoLFF. JAMES E. HoLLYnAY.

Witnesses:

HARRYv S. PLATOWSKY, N. J. STORM..

